Process for preparing Z-endoxifen of high purity

Disclosed is a process for preparing (Z)-endoxifen, comprising (i) recrystallizing an input crystalline solid comprising a mixture of (Z)-endoxifen (1) and (E)-endoxifen (2) from a first solvent to provide a first crystalline solid and a first mother liquor, wherein the first mother liquor has a ratio of (1) to (2) at least 1.3 times greater than the ratio in the input crystalline solid (1) and (2); (ii) recrystallizing a solid produced by concentrating the first mother liquor, or by removal of the first solvent from the first mother liquor, from a second solvent to give a second crystalline solid and a second mother liquor; (iii) optionally recrystallizing the second crystalline solid from the second solvent one to five additional times to give a third crystalline solid; wherein the third crystalline solid has a ratio of (Z)-endoxifen (1) to (E)-endoxifen (2) greater than 20:1.